Alloy steels



United States Patent 3,155,500 ALLOY STEELS Harry L. Anthony m and Gopal K. Bhat, Pittsburgh, Pa., assignors, by mesne assignments, to Wilson Brothers, New York, N .Y., a corporation of Illinois No Drawing. Original application May 29, 1959, Ser. No. 817,447. Divided and this application July 18, 1962, Ser. No. 210,824

3 Claims. (Cl. 75-126) This application is a division of our co-pending application Serial No. 817,447, filed May 29, 1959.

Modern developments in missiles, aircraft, high strength pressure vessels and the like require alloy steels having high yield strength levels. These high yield strength levels have in the past been deemed obtainable only by the use of special steels having relatively high concentrations of alloying elements such as the H-ll hot work tool and die steels and the like. These tool and die steels, however, have many drawbacks. They require special care in their manufacture and in their heat treatment. The segregation of complex alloy carbides and particularly the control of their size and distribution during heat treatment is diflicult. Welding of such steels poses diflicult problems to fabricators, and uniform hardness is difficult to attain.

We have discovered an alloy steel composition which reduces these problems and attains the high yield strength levels desired without the need for relatively large quantities of alloying elements.

We provide an alloy having a composition within the following limits:

Carbon About 0.35% to about 0.45%.

Manganese About 0.60% to about 1.10%.

Phosphorus 0.025% maximum.

Sulfur 0.025% maximum.

Silicon About 0.60% to about 1.50%.

Chromium About 0.80% to about 1.50%.

Molybdenum About 0.15% to about 0.40%.

Tungsten May be substituted for molybdenum in ratio of 2:1.

Vanadium About 0.10% to about 0.25%.

Cobalt About 0.85% to about 1.34% but may be absent when vanadium is above 0.15%.

Balance iron with usual impurities in ordinary amounts.

In a preferred composition of our alloy we provide:

Percent Carbon About 0.40 Manganese About 0.70 Phosphorus About 0.010 Sulfur About 0.010 Silicon About 0.80 Chromium About 1.00 Molybdenum About 0.20 Vanadium About 0.10 Cobalt About 1.00

Balance iron with usual impurities in ordinary amounts.

We have melted and tested several heats of steel made according to our invention and have found that in every case they had the high yield strength level desired as well as a large differential between offset yield strength and ultimate tensile strength.

3,155,500 Patented Nov. 3, 1964 Example I A 4,000 pound heat of steel was made of the following composition:

Percent Carbon 0.38 Manganese 0.70

Sulfur 0.020 Phosphorus 0.020 Silicon 1.00 Chromium 0.90 Molybdenum 0.25 Vanadium 0.10 Cobalt 1.00

Balance iron with usual impurities in ordinary amounts.

This material was formed into bars and sheets and tested. The material, after being austenitized at 1700 F., quenched in oil and tempered at 600 F., gave the following physical values:

0.2% offset yield strength About 232,000 p.s.i. Ultimate tensile strength About 272,000 p.s.i. Elongation, in two inches About 5.5% to about 6.5%.

The same results were obtained when the quenching was done in molten salt at 400 F. and tempered as above.

Example II A 4,000 pound heat of steel was melted in an electric Balance iron with usual impurities in ordinary amounts.

This material was heat treated as in Example I and gave the following physical values:

0.2% offset yield strenth About 227,000 p.s.i. Ultimate tensile strength About 279,000 p.s.i. Elongation, in two inches About 6.0%.

Example III A 1,000 pound heat of steel was melted to a composition of Percent Carbon 0.41 Manganese 0.72 Sulfur 0.012 Phosphorus 0.014 Silicon V 0.88 Chromium 1.31 Molybdenum 0.27 Vanadium 0.10 Cobalt 0.92

Balance iron with usual impurities in ordinary amounts.

Bars and sheets were formed, heat treated and tested as in Example I and gave the following physical values:

0.2% offset yield strength About 226,000 p.s.i. Ultimate tensile strength About 267,000 p.s.i. Elongation, in two inches About 6.5%.

Example I V A heat was made according to the following analysis:

Percent Carbon 0.44

Managanese 0.54 Sulfur 0.006

Phosphorus 0.017 Silicon 1.51

Chromium 1.20

Molybdenum 0.30 Vanadium 0.14

Cobalt t 1.34

Balance iron with usual impurities in ordinary amounts.

Physical values of bars and sheets tested as in Example I were:

P.s.i. 0.2% offset yield strength About 265,000 Ultimate tensile strength About 300,000

A comparison of the 0.2% offset yield strength with the ultimate strength shows the broad range between the two.

Similar but not as good results can be obtained by increasing the vanadium content above about 0.15% to about 0.25% and reducing or entirely eliminating the cobalt content. For example, a heat of steel was 155% to the composition:

Balance iron with usual impurities in ordinary amounts.

The above alloy was formed, treated and tested as in Example I and gave the following physical values:

0.2% offset yield strength About 213,000 p.s.i. Ultimate tensile strength About 267,000 p.s.i. Elongation, in two inches About 4.0% to about 5.5%.

We have found that tungsten can be substituted for part or all of the molybdenum in the ratio of two parts of tungsten to one part of molybdenum.

The following heat of steel was made:

Example VI Percent Carbon 0.47 Manganese 5.--. 1.20 Sulfur 0.007 Phosphorus 0.006 Silicon 1.23 Chromium 1.46

Vanadium 0.19

Cobalt 1.02

Tungsten 0.62

Balance iron with usual impurities in ordinary amounts.

4 Physical values of bars and sheets tested as in Example I were:

0.2% offset yield strength About 249,000 p.s.i. Ultimate tensile strength About 297,000 p.s.i. Elongation, in two inches About 7.5%.

Material from the foregoing examples was reverse drawn into thin walled missile cases with satisfactory results. Except for the steel in which tungsten was substituted for molybdenum (Example VI above), which was not fabricated, the material was welded without any of the difiiculties which had characterized the cases made of Hl1 hot work tool steels.

While we have illustrated and described certain preferred compositions and practices of our invention, it will be understood that this invention may be otherwise embodied within the scope of the following claims.

We claim:

1. A high strength rolled alloy steel comprising carbon about 0.35% to about 0.43%, manganese about 0.60% to about 1.10%, phosphorus about 0.025% maximum, sulfur about 0.025% maximum, silicon about 0.60% to about 1.09%, chromium about 0.80% to about 1.36%, molybdenum about 0.15% to about 0.27%, vanadium about 0.15% to about 0.25%, and the balance iron with usual impurities in ordinary amounts, austenitized at about 1700 F., quenched at about 400 F., and tempered at about 600 F., said rolled alloy steel being characterized by good weldability and freedom from carbide segregation, and, after being so heat treated, being characterized by a 0.2% offset yield strength in excess of about 213,000 p.s.i. and an ultimate tensile strength about 40,000 p.s.i. greater than the yield strength.

2. A high strength missile motor case made from a rolled alloy steel comprising carbon about 0.35% to about 0.43%, manganese about 0.60% to about 1.10%, phosphorus about 0.025% maximum, sulfur about 0.025% maximum, silicon about 0.60% to about 1.09%, chromium about 0.80% to about 1.36%, molybdenum about 0.15% to about 0.27%, vanadium about 0.15% to about 0.25%, and the balance iron with usual impurities in ordinary amounts, said missile motor case being characterized by a 0.2% offset yield strength in excess of about 213,000 p.s.i. and an ultimate tensile strength about 40,000 p.s.i. greater than the yield strength.

3. A high strength article made from a rolled alloy comprising carbon about 0.35 to about 0.43%, manganese about 0.60% to about 1.10%, phosphorus about 0.025% maximum, sulfur about 0.025% maximum, silicon about 0.60% to about 1.09%, chromium about 0.80% to about 1.36%, molybdenum about 0.15% to about 0.27%, vanadium about 0.15% to about 0.25%, and the balance iron with usual impurities in ordinary amounts, said article being characterized by a 0.2% oilset yield strength in excess of about 213,000 p.s.i. and an ultimate tensile strength about 40,000 p.s.i. greater than the yield strength.

References Cited by the Examiner UNITED STATES PATENTS 11/35 Hildorf -126 7/53 Clark 75126 

2. A HIGH STRENGTH MISSILE MOTOR CASE MADE FROM A ROLLED ALLOY STEEL COMPRISING CARBON ABOUT 0.35% TO ABOUT 0.43%, MANGANESE ABOUT 0.60% TO ABOUT 1.10%, PHOSPHORUS ABOUT 0.025% MAXIMUM, SULFUR ABOUT 0.025% MAXIMUM, SILICON ABOUT 0.60% TO ABOUT 1.09%, CHROMIUM ABOUT 0.80% TO ABOUT 1.36%, MOLYBDENUM ABOUT 0.15% TO ABOUT 0.27%, VANADIUM AB OUT 0.15% TO ABOUT 0.25%, AND THE BALANCE IRON WITH USUAL IMPURITIES IN ORDINARY AMOUNTS, SAID MISSILE MOTOR CASE BEING CHARACTERIZED BY A 0.2% OFFSET YIELD STRENGTH IN EXCESS OF ABOUT 213,000 P.S.I. AND AN ULTIMATE TENSILE STRENGTH ABOUT 40,000 P.S.I. GREATER THAN THE YIELD STRENGTH. 